Chlorine is often added to drinking water supplies to kill harmful microorganisms. Chlorine is not only an effective disinfectant, but it also reacts with ammonia, iron and other metals and some organic compounds to improve overall water quality. There is a limit to the use of chlorine, however, as negative results are possible with the addition of too much chlorine. Bad tastes or odors in water are often enhanced. Excess chlorine can be harmful to fish and other aquatic animals when the water contains nitrogen compounds. Finally, the formation of chloroform and other suspected carcinogens is possible. It is thus very important for water suppliers to monitor closely the levels of chlorine present in the water for which they are responsible. Practically, water systems look for a level of chlorine remaining in the water after treatment to be 1 mg/L or less for minimizing adverse effects while maintaining disinfectant properties. Above 1 mg/L, odor and taste often become problematic.
A method and apparatus for the measurement of amounts of free available chlorine in solution have been described in U.S. Pat. No. 3,956,094 and other patents. The apparatus includes a sensing electrode, which is internally, and a reference electrode supported within a container. The electrode surface is continuously washed by the pH control solution. The method and apparatus of the present invention is adapted to be used, for example, to measure the free available chlorine concentration in swimming pool waters. Nevertheless, the dependency on said fragile and ever blockaged sensing electrode, as well as the requirement for a routine cleansing operation, which usually requires manually routine of disintegrating the assembly accommodating the electrode, cleansing operation and vis versa eliminates the use of said method.
Yet another and more efficient method was presented, see for example U.S. Pat. No. 6,180,412 to determine photometrically chlorine concentration in water. The method of determining chlorine in this experiment relies on a color indicator, usually N,N-diethyl-p-phenylene-diamine, denoted in its short and known term ‘DPD’. In the presence of chlorine, DPD reacts rapidly to form a red color, the intensity of which is an indicator of chlorine concentration. The higher the absorbance, the higher the chlorine concentration. Thought the photochemical reaction is pH sensitive, DPD/chlorine system typically appears in a red color, measured at about 515 nm. At a near neutral pH, the primary oxidation product is a semi-quinoid cationic compound known as a Wurster dye. The DPD Wurster dye color has been measured photo-metrically at wavelengths ranging from 490 to 555 nm.
A measuring cell useful for a routine determination of fluids, having mechanical means to clean the inner core of the measurement cell was not presented in art. It is thus the aim of the present invention to provide a novel spectrophotometric measuring cell, useful for automated reagent mixing and for handsfree physical cleansing.